This invention relates to motion-transmitting arrangements.
The invention can be used to particular advantage in windshield wiping arrangements for vehicles (but is not limited thereto) and will, therefore, hereafter be described in the context of such a windshield wiping arrangement for a ready understanding.
Windshield wiping arrangements have been proposed wherein a rotary output shaft of a drive turns a crank which carries, laterally spaced from the output shaft, a crankpin. One end of a crank rod is pivotally connected to the crankpin and the other end is pivoted to one end of a link member whose other end is in turn pivoted on a fixed pivot point. A wiper blade is connected-- usually indirectly-- to the link member so as to move and wipe an area of a vehicle windshield, when the link member is pivoted to and fro by operation of the crank.
It has been found that in this otherwise satisfactory construction problems are encountered when the manufacturing tolerances for the component parts are not precisely maintained. This is, of course, not economically feasible in such mass-production articles with the result that, especially when the tolerance variations of all component parts add up together, the area wiped by the wiper blade may be either smaller or larger than intended. As every vehicle operator knows, this either means that unwiped (i.e., dirty) windshield portions remain between the edge of the windshield and the position at which the wiper blade movement is reversed, or that the wiper blade moves onto the frame of the windshield. The former reduces the vision area of the vehicle operator and constitutes a safety hazard; the latter results in premature damage and wear of the wiper blade and, since such wear often remains undetected (or at least uncorrected) for relatively long periods of time, ultimately also constitutes a safety hazard because a worn wiper blade will not give satisfactory wiping results.
Such problems do not necessarily occur immediately upon installation of the windshield wiping arrangement; quite frequently they come about only after the arrangement has been in use for a period of time, usually due to wear (and resulting play) in the pivots and journals of the movable components.